text: /*
   *	Handle firewalling
   *	Linux ethernet bridge
   *
   *	Authors:
   *	Lennert Buytenhek		<buytenh@gnu.org>
   *	Bart De Schuymer		<bdschuym@pandora.be>
   *
   *	This program is free software; you can redistribute it and/or
   *	modify it under the terms of the GNU General Public License
   *	as published by the Free Software Foundation; either version
   *	2 of the License, or (at your option) any later version.
   *
   *	Lennert dedicates this file to Kerstin Wurdinger.
   */
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/slab.h>
  #include <linux/ip.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>
  #include <linux/if_arp.h>
  #include <linux/if_ether.h>
  #include <linux/if_vlan.h>
  #include <linux/if_pppox.h>
  #include <linux/ppp_defs.h>
  #include <linux/netfilter_bridge.h>
  #include <linux/netfilter_ipv4.h>
  #include <linux/netfilter_ipv6.h>
  #include <linux/netfilter_arp.h>
  #include <linux/in_route.h>
  #include <linux/rculist.h>
  #include <linux/inetdevice.h>
  
  #include <net/ip.h>
  #include <net/ipv6.h>
  #include <net/addrconf.h>
  #include <net/route.h>
  #include <net/netfilter/br_netfilter.h>
  #include <net/netns/generic.h>
  
  #include <linux/uaccess.h>
  #include "br_private.h"
  #ifdef CONFIG_SYSCTL
  #include <linux/sysctl.h>
  #endif
  
  static unsigned int brnf_net_id __read_mostly;
  
  struct brnf_net {
  	bool enabled;
  };
  
  #ifdef CONFIG_SYSCTL
  static struct ctl_table_header *brnf_sysctl_header;
  static int brnf_call_iptables __read_mostly = 1;
  static int brnf_call_ip6tables __read_mostly = 1;
  static int brnf_call_arptables __read_mostly = 1;
  static int brnf_filter_vlan_tagged __read_mostly;
  static int brnf_filter_pppoe_tagged __read_mostly;
  static int brnf_pass_vlan_indev __read_mostly;
  #else
  #define brnf_call_iptables 1
  #define brnf_call_ip6tables 1
  #define brnf_call_arptables 1
  #define brnf_filter_vlan_tagged 0
  #define brnf_filter_pppoe_tagged 0
  #define brnf_pass_vlan_indev 0
  #endif
  
  #define IS_IP(skb) \
  	(!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_IP))
  
  #define IS_IPV6(skb) \
  	(!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_IPV6))
  
  #define IS_ARP(skb) \
  	(!skb_vlan_tag_present(skb) && skb->protocol == htons(ETH_P_ARP))
  
  static inline __be16 vlan_proto(const struct sk_buff *skb)
  {
  	if (skb_vlan_tag_present(skb))
  		return skb->protocol;
  	else if (skb->protocol == htons(ETH_P_8021Q))
  		return vlan_eth_hdr(skb)->h_vlan_encapsulated_proto;
  	else
  		return 0;
  }
  
  #define IS_VLAN_IP(skb) \
  	(vlan_proto(skb) == htons(ETH_P_IP) && \
  	 brnf_filter_vlan_tagged)
  
  #define IS_VLAN_IPV6(skb) \
  	(vlan_proto(skb) == htons(ETH_P_IPV6) && \
  	 brnf_filter_vlan_tagged)
  
  #define IS_VLAN_ARP(skb) \
  	(vlan_proto(skb) == htons(ETH_P_ARP) &&	\
  	 brnf_filter_vlan_tagged)
  
  static inline __be16 pppoe_proto(const struct sk_buff *skb)
  {
  	return *((__be16 *)(skb_mac_header(skb) + ETH_HLEN +
  			    sizeof(struct pppoe_hdr)));
  }
  
  #define IS_PPPOE_IP(skb) \
  	(skb->protocol == htons(ETH_P_PPP_SES) && \
  	 pppoe_proto(skb) == htons(PPP_IP) && \
  	 brnf_filter_pppoe_tagged)
  
  #define IS_PPPOE_IPV6(skb) \
  	(skb->protocol == htons(ETH_P_PPP_SES) && \
  	 pppoe_proto(skb) == htons(PPP_IPV6) && \
  	 brnf_filter_pppoe_tagged)
  
  /* largest possible L2 header, see br_nf_dev_queue_xmit() */
  #define NF_BRIDGE_MAX_MAC_HEADER_LENGTH (PPPOE_SES_HLEN + ETH_HLEN)
  
  struct brnf_frag_data {
  	char mac[NF_BRIDGE_MAX_MAC_HEADER_LENGTH];
  	u8 encap_size;
  	u8 size;
  	u16 vlan_tci;
  	__be16 vlan_proto;
  };
  
  static DEFINE_PER_CPU(struct brnf_frag_data, brnf_frag_data_storage);
  
  static void nf_bridge_info_free(struct sk_buff *skb)
  {
  	if (skb->nf_bridge) {
  		nf_bridge_put(skb->nf_bridge);
  		skb->nf_bridge = NULL;
  	}
  }
  
  static inline struct net_device *bridge_parent(const struct net_device *dev)
  {
  	struct net_bridge_port *port;
  
  	port = br_port_get_rcu(dev);
  	return port ? port->br->dev : NULL;
  }
  
  static inline struct nf_bridge_info *nf_bridge_unshare(struct sk_buff *skb)
  {
  	struct nf_bridge_info *nf_bridge = skb->nf_bridge;
  
  	if (refcount_read(&nf_bridge->use) > 1) {
  		struct nf_bridge_info *tmp = nf_bridge_alloc(skb);
  
  		if (tmp) {
  			memcpy(tmp, nf_bridge, sizeof(struct nf_bridge_info));
  			refcount_set(&tmp->use, 1);
  		}
  		nf_bridge_put(nf_bridge);
  		nf_bridge = tmp;
  	}
  	return nf_bridge;
  }
  
  unsigned int nf_bridge_encap_header_len(const struct sk_buff *skb)
  {
  	switch (skb->protocol) {
  	case __cpu_to_be16(ETH_P_8021Q):
  		return VLAN_HLEN;
  	case __cpu_to_be16(ETH_P_PPP_SES):
  		return PPPOE_SES_HLEN;
  	default:
  		return 0;
  	}
  }
  
  static inline void nf_bridge_pull_encap_header(struct sk_buff *skb)
  {
  	unsigned int len = nf_bridge_encap_header_len(skb);
  
  	skb_pull(skb, len);
  	skb->network_header += len;
  }
  
  static inline void nf_bridge_pull_encap_header_rcsum(struct sk_buff *skb)
  {
  	unsigned int len = nf_bridge_encap_header_len(skb);
  
  	skb_pull_rcsum(skb, len);
  	skb->network_header += len;
  }
  
  /* When handing a packet over to the IP layer
   * check whether we have a skb that is in the
   * expected format
   */
  
  static int br_validate_ipv4(struct net *net, struct sk_buff *skb)
  {
  	const struct iphdr *iph;
  	u32 len;
  
  	if (!pskb_may_pull(skb, sizeof(struct iphdr)))
  		goto inhdr_error;
  
  	iph = ip_hdr(skb);
  
  	/* Basic sanity checks */
  	if (iph->ihl < 5 || iph->version != 4)
  		goto inhdr_error;
  
  	if (!pskb_may_pull(skb, iph->ihl*4))
  		goto inhdr_error;
  
  	iph = ip_hdr(skb);
  	if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
  		goto inhdr_error;
  
  	len = ntohs(iph->tot_len);
  	if (skb->len < len) {
  		__IP_INC_STATS(net, IPSTATS_MIB_INTRUNCATEDPKTS);
  		goto drop;
  	} else if (len < (iph->ihl*4))
  		goto inhdr_error;
  
  	if (pskb_trim_rcsum(skb, len)) {
  		__IP_INC_STATS(net, IPSTATS_MIB_INDISCARDS);
  		goto drop;
  	}
  
  	memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
  	/* We should really parse IP options here but until
  	 * somebody who actually uses IP options complains to
  	 * us we'll just silently ignore the options because
  	 * we're lazy!
  	 */
  	return 0;
  
  inhdr_error:
  	__IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS);
  drop:
  	return -1;
  }
  
  void nf_bridge_update_protocol(struct sk_buff *skb)
  {
  	switch (skb->nf_bridge->orig_proto) {
  	case BRNF_PROTO_8021Q:
  		skb->protocol = htons(ETH_P_8021Q);
  		break;
  	case BRNF_PROTO_PPPOE:
  		skb->protocol = htons(ETH_P_PPP_SES);
  		break;
  	case BRNF_PROTO_UNCHANGED:
  		break;
  	}
  }
  
  /* Obtain the correct destination MAC address, while preserving the original
   * source MAC address. If we already know this address, we just copy it. If we
   * don't, we use the neighbour framework to find out. In both cases, we make
   * sure that br_handle_frame_finish() is called afterwards.
   */
  int br_nf_pre_routing_finish_bridge(struct net *net, struct sock *sk, struct sk_buff *skb)
  {
  	struct neighbour *neigh;
  	struct dst_entry *dst;
  
  	skb->dev = bridge_parent(skb->dev);
  	if (!skb->dev)
  		goto free_skb;
  	dst = skb_dst(skb);
  	neigh = dst_neigh_lookup_skb(dst, skb);
  	if (neigh) {
  		struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
  		int ret;
  
  		if (neigh->hh.hh_len) {
  			neigh_hh_bridge(&neigh->hh, skb);
  			skb->dev = nf_bridge->physindev;
  			ret = br_handle_frame_finish(net, sk, skb);
  		} else {
  			/* the neighbour function below overwrites the complete
  			 * MAC header, so we save the Ethernet source address and
  			 * protocol number.
  			 */
  			skb_copy_from_linear_data_offset(skb,
  							 -(ETH_HLEN-ETH_ALEN),
  							 nf_bridge->neigh_header,
  							 ETH_HLEN-ETH_ALEN);
  			/* tell br_dev_xmit to continue with forwarding */
  			nf_bridge->bridged_dnat = 1;
  			/* FIXME Need to refragment */
  			ret = neigh->output(neigh, skb);
  		}
  		neigh_release(neigh);
  		return ret;
  	}
  free_skb:
  	kfree_skb(skb);
  	return 0;
  }
  
  static inline bool
  br_nf_ipv4_daddr_was_changed(const struct sk_buff *skb,
  			     const struct nf_bridge_info *nf_bridge)
  {
  	return ip_hdr(skb)->daddr != nf_bridge->ipv4_daddr;
  }
  
  /* This requires some explaining. If DNAT has taken place,
   * we will need to fix up the destination Ethernet address.
   * This is also true when SNAT takes place (for the reply direction).
   *
   * There are two cases to consider:
   * 1. The packet was DNAT'ed to a device in the same bridge
   *    port group as it was received on. We can still bridge
   *    the packet.
   * 2. The packet was DNAT'ed to a different device, either
   *    a non-bridged device or another bridge port group.
   *    The packet will need to be routed.
   *
   * The correct way of distinguishing between these two cases is to
   * call ip_route_input() and to look at skb->dst->dev, which is
   * changed to the destination device if ip_route_input() succeeds.
   *
   * Let's first consider the case that ip_route_input() succeeds:
   *
   * If the output device equals the logical bridge device the packet
   * came in on, we can consider this bridging. The corresponding MAC
   * address will be obtained in br_nf_pre_routing_finish_bridge.
   * Otherwise, the packet is considered to be routed and we just
   * change the destination MAC address so that the packet will
   * later be passed up to the IP stack to be routed. For a redirected
   * packet, ip_route_input() will give back the localhost as output device,
   * which differs from the bridge device.
   *
   * Let's now consider the case that ip_route_input() fails:
   *
   * This can be because the destination address is martian, in which case
   * the packet will be dropped.
   * If IP forwarding is disabled, ip_route_input() will fail, while
   * ip_route_output_key() can return success. The source
   * address for ip_route_output_key() is set to zero, so ip_route_output_key()
   * thinks we're handling a locally generated packet and won't care
   * if IP forwarding is enabled. If the output device equals the logical bridge
   * device, we proceed as if ip_route_input() succeeded. If it differs from the
   * logical bridge port or if ip_route_output_key() fails we drop the packet.
   */
  static int br_nf_pre_routing_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
  {
  	struct net_device *dev = skb->dev;
  	struct iphdr *iph = ip_hdr(skb);
  	struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
  	struct rtable *rt;
  	int err;
  
  	nf_bridge->frag_max_size = IPCB(skb)->frag_max_size;
  
  	if (nf_bridge->pkt_otherhost) {
  		skb->pkt_type = PACKET_OTHERHOST;
  		nf_bridge->pkt_otherhost = false;
  	}
  	nf_bridge->in_prerouting = 0;
  	if (br_nf_ipv4_daddr_was_changed(skb, nf_bridge)) {
  		if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) {
  			struct in_device *in_dev = __in_dev_get_rcu(dev);
  
  			/* If err equals -EHOSTUNREACH the error is due to a
  			 * martian destination or due to the fact that
  			 * forwarding is disabled. For most martian packets,
  			 * ip_route_output_key() will fail. It won't fail for 2 types of
  			 * martian destinations: loopback destinations and destination
  			 * 0.0.0.0. In both cases the packet will be dropped because the
  			 * destination is the loopback device and not the bridge. */
  			if (err != -EHOSTUNREACH || !in_dev || IN_DEV_FORWARD(in_dev))
  				goto free_skb;
  
  			rt = ip_route_output(net, iph->daddr, 0,
  					     RT_TOS(iph->tos), 0);
  			if (!IS_ERR(rt)) {
  				/* - Bridged-and-DNAT'ed traffic doesn't
  				 *   require ip_forwarding. */
  				if (rt->dst.dev == dev) {
  					skb_dst_set(skb, &rt->dst);
  					goto bridged_dnat;
  				}
  				ip_rt_put(rt);
  			}
  free_skb:
  			kfree_skb(skb);
  			return 0;
  		} else {
  			if (skb_dst(skb)->dev == dev) {
  bridged_dnat:
  				skb->dev = nf_bridge->physindev;
  				nf_bridge_update_protocol(skb);
  				nf_bridge_push_encap_header(skb);
  				br_nf_hook_thresh(NF_BR_PRE_ROUTING,
  						  net, sk, skb, skb->dev,
  						  NULL,
  						  br_nf_pre_routing_finish_bridge);
  				return 0;
  			}
  			ether_addr_copy(eth_hdr(skb)->h_dest, dev->dev_addr);
  			skb->pkt_type = PACKET_HOST;
  		}
  	} else {
  		rt = bridge_parent_rtable(nf_bridge->physindev);
  		if (!rt) {
  			kfree_skb(skb);
  			return 0;
  		}
  		skb_dst_set_noref(skb, &rt->dst);
  	}
  
  	skb->dev = nf_bridge->physindev;
  	nf_bridge_update_protocol(skb);
  	nf_bridge_push_encap_header(skb);
  	br_nf_hook_thresh(NF_BR_PRE_ROUTING, net, sk, skb, skb->dev, NULL,
  			  br_handle_frame_finish);
  	return 0;
  }
  
  static struct net_device *brnf_get_logical_dev(struct sk_buff *skb, const struct net_device *dev)
  {
  	struct net_device *vlan, *br;
  
  	br = bridge_parent(dev);
  	if (brnf_pass_vlan_indev == 0 || !skb_vlan_tag_present(skb))
  		return br;
  
  	vlan = __vlan_find_dev_deep_rcu(br, skb->vlan_proto,
  				    skb_vlan_tag_get(skb) & VLAN_VID_MASK);
  
  	return vlan ? vlan : br;
  }
  
  /* Some common code for IPv4/IPv6 */
  struct net_device *setup_pre_routing(struct sk_buff *skb)
  {
  	struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
  
  	if (skb->pkt_type == PACKET_OTHERHOST) {
  		skb->pkt_type = PACKET_HOST;
  		nf_bridge->pkt_otherhost = true;
  	}
  
  	nf_bridge->in_prerouting = 1;
  	nf_bridge->physindev = skb->dev;
  	skb->dev = brnf_get_logical_dev(skb, skb->dev);
  
  	if (skb->protocol == htons(ETH_P_8021Q))
  		nf_bridge->orig_proto = BRNF_PROTO_8021Q;
  	else if (skb->protocol == htons(ETH_P_PPP_SES))
  		nf_bridge->orig_proto = BRNF_PROTO_PPPOE;
  
  	/* Must drop socket now because of tproxy. */
  	skb_orphan(skb);
  	return skb->dev;
  }
  
  /* Direct IPv6 traffic to br_nf_pre_routing_ipv6.
   * Replicate the checks that IPv4 does on packet reception.
   * Set skb->dev to the bridge device (i.e. parent of the
   * receiving device) to make netfilter happy, the REDIRECT
   * target in particular.  Save the original destination IP
   * address to be able to detect DNAT afterwards. */
  static unsigned int br_nf_pre_routing(void *priv,
  				      struct sk_buff *skb,
  				      const struct nf_hook_state *state)
  {
  	struct nf_bridge_info *nf_bridge;
  	struct net_bridge_port *p;
  	struct net_bridge *br;
  	__u32 len = nf_bridge_encap_header_len(skb);
  
  	if (unlikely(!pskb_may_pull(skb, len)))
  		return NF_DROP;
  
  	p = br_port_get_rcu(state->in);
  	if (p == NULL)
  		return NF_DROP;
  	br = p->br;
  
  	if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb)) {
  		if (!brnf_call_ip6tables && !br->nf_call_ip6tables)
  			return NF_ACCEPT;
  
  		nf_bridge_pull_encap_header_rcsum(skb);
  		return br_nf_pre_routing_ipv6(priv, skb, state);
  	}
  
  	if (!brnf_call_iptables && !br->nf_call_iptables)
  		return NF_ACCEPT;
  
  	if (!IS_IP(skb) && !IS_VLAN_IP(skb) && !IS_PPPOE_IP(skb))
  		return NF_ACCEPT;
  
  	nf_bridge_pull_encap_header_rcsum(skb);
  
  	if (br_validate_ipv4(state->net, skb))
  		return NF_DROP;
  
  	nf_bridge_put(skb->nf_bridge);
  	if (!nf_bridge_alloc(skb))
  		return NF_DROP;
  	if (!setup_pre_routing(skb))
  		return NF_DROP;
  
  	nf_bridge = nf_bridge_info_get(skb);
  	nf_bridge->ipv4_daddr = ip_hdr(skb)->daddr;
  
  	skb->protocol = htons(ETH_P_IP);
  
  	NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, state->net, state->sk, skb,
  		skb->dev, NULL,
  		br_nf_pre_routing_finish);
  
  	return NF_STOLEN;
  }
  
  
  /* PF_BRIDGE/FORWARD *************************************************/
  static int br_nf_forward_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
  {
  	struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
  	struct net_device *in;
  
  	if (!IS_ARP(skb) && !IS_VLAN_ARP(skb)) {
  
  		if (skb->protocol == htons(ETH_P_IP))
  			nf_bridge->frag_max_size = IPCB(skb)->frag_max_size;
  
  		if (skb->protocol == htons(ETH_P_IPV6))
  			nf_bridge->frag_max_size = IP6CB(skb)->frag_max_size;
  
  		in = nf_bridge->physindev;
  		if (nf_bridge->pkt_otherhost) {
  			skb->pkt_type = PACKET_OTHERHOST;
  			nf_bridge->pkt_otherhost = false;
  		}
  		nf_bridge_update_protocol(skb);
  	} else {
  		in = *((struct net_device **)(skb->cb));
  	}
  	nf_bridge_push_encap_header(skb);
  
  	br_nf_hook_thresh(NF_BR_FORWARD, net, sk, skb, in, skb->dev,
  			  br_forward_finish);
  	return 0;
  }
  
  
  /* This is the 'purely bridged' case.  For IP, we pass the packet to
   * netfilter with indev and outdev set to the bridge device,
   * but we are still able to filter on the 'real' indev/outdev
   * because of the physdev module. For ARP, indev and outdev are the
   * bridge ports. */
  static unsigned int br_nf_forward_ip(void *priv,
  				     struct sk_buff *skb,
  				     const struct nf_hook_state *state)
  {
  	struct nf_bridge_info *nf_bridge;
  	struct net_device *parent;
  	u_int8_t pf;
  
  	if (!skb->nf_bridge)
  		return NF_ACCEPT;
  
  	/* Need exclusive nf_bridge_info since we might have multiple
  	 * different physoutdevs. */
  	if (!nf_bridge_unshare(skb))
  		return NF_DROP;
  
  	nf_bridge = nf_bridge_info_get(skb);
  	if (!nf_bridge)
  		return NF_DROP;
  
  	parent = bridge_parent(state->out);
  	if (!parent)
  		return NF_DROP;
  
  	if (IS_IP(skb) || IS_VLAN_IP(skb) || IS_PPPOE_IP(skb))
  		pf = NFPROTO_IPV4;
  	else if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb))
  		pf = NFPROTO_IPV6;
  	else
  		return NF_ACCEPT;
  
  	nf_bridge_pull_encap_header(skb);
  
  	if (skb->pkt_type == PACKET_OTHERHOST) {
  		skb->pkt_type = PACKET_HOST;
  		nf_bridge->pkt_otherhost = true;
  	}
  
  	if (pf == NFPROTO_IPV4) {
  		if (br_validate_ipv4(state->net, skb))
  			return NF_DROP;
  		IPCB(skb)->frag_max_size = nf_bridge->frag_max_size;
  	}
  
  	if (pf == NFPROTO_IPV6) {
  		if (br_validate_ipv6(state->net, skb))
  			return NF_DROP;
  		IP6CB(skb)->frag_max_size = nf_bridge->frag_max_size;
  	}
  
  	nf_bridge->physoutdev = skb->dev;
  	if (pf == NFPROTO_IPV4)
  		skb->protocol = htons(ETH_P_IP);
  	else
  		skb->protocol = htons(ETH_P_IPV6);
  
  	NF_HOOK(pf, NF_INET_FORWARD, state->net, NULL, skb,
  		brnf_get_logical_dev(skb, state->in),
  		parent,	br_nf_forward_finish);
  
  	return NF_STOLEN;
  }
  
  static unsigned int br_nf_forward_arp(void *priv,
  				      struct sk_buff *skb,
  				      const struct nf_hook_state *state)
  {
  	struct net_bridge_port *p;
  	struct net_bridge *br;
  	struct net_device **d = (struct net_device **)(skb->cb);
  
  	p = br_port_get_rcu(state->out);
  	if (p == NULL)
  		return NF_ACCEPT;
  	br = p->br;
  
  	if (!brnf_call_arptables && !br->nf_call_arptables)
  		return NF_ACCEPT;
  
  	if (!IS_ARP(skb)) {
  		if (!IS_VLAN_ARP(skb))
  			return NF_ACCEPT;
  		nf_bridge_pull_encap_header(skb);
  	}
  
  	if (arp_hdr(skb)->ar_pln != 4) {
  		if (IS_VLAN_ARP(skb))
  			nf_bridge_push_encap_header(skb);
  		return NF_ACCEPT;
  	}
  	*d = state->in;
  	NF_HOOK(NFPROTO_ARP, NF_ARP_FORWARD, state->net, state->sk, skb,
  		state->in, state->out, br_nf_forward_finish);
  
  	return NF_STOLEN;
  }
  
  static int br_nf_push_frag_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
  {
  	struct brnf_frag_data *data;
  	int err;
  
  	data = this_cpu_ptr(&brnf_frag_data_storage);
  	err = skb_cow_head(skb, data->size);
  
  	if (err) {
  		kfree_skb(skb);
  		return 0;
  	}
  
  	if (data->vlan_tci) {
  		skb->vlan_tci = data->vlan_tci;
  		skb->vlan_proto = data->vlan_proto;
  	}
  
  	skb_copy_to_linear_data_offset(skb, -data->size, data->mac, data->size);
  	__skb_push(skb, data->encap_size);
  
  	nf_bridge_info_free(skb);
  	return br_dev_queue_push_xmit(net, sk, skb);
  }
  
  static int
  br_nf_ip_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
  		  int (*output)(struct net *, struct sock *, struct sk_buff *))
  {
  	unsigned int mtu = ip_skb_dst_mtu(sk, skb);
  	struct iphdr *iph = ip_hdr(skb);
  
  	if (unlikely(((iph->frag_off & htons(IP_DF)) && !skb->ignore_df) ||
  		     (IPCB(skb)->frag_max_size &&
  		      IPCB(skb)->frag_max_size > mtu))) {
  		IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS);
  		kfree_skb(skb);
  		return -EMSGSIZE;
  	}
  
  	return ip_do_fragment(net, sk, skb, output);
  }
  
  static unsigned int nf_bridge_mtu_reduction(const struct sk_buff *skb)
  {
  	if (skb->nf_bridge->orig_proto == BRNF_PROTO_PPPOE)
  		return PPPOE_SES_HLEN;
  	return 0;
  }
  
  static int br_nf_dev_queue_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
  {
  	struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
  	unsigned int mtu, mtu_reserved;
  
  	mtu_reserved = nf_bridge_mtu_reduction(skb);
  	mtu = skb->dev->mtu;
  
  	if (nf_bridge->frag_max_size && nf_bridge->frag_max_size < mtu)
  		mtu = nf_bridge->frag_max_size;
  
  	if (skb_is_gso(skb) || skb->len + mtu_reserved <= mtu) {
  		nf_bridge_info_free(skb);
  		return br_dev_queue_push_xmit(net, sk, skb);
  	}
  
  	/* This is wrong! We should preserve the original fragment
  	 * boundaries by preserving frag_list rather than refragmenting.
  	 */
  	if (IS_ENABLED(CONFIG_NF_DEFRAG_IPV4) &&
  	    skb->protocol == htons(ETH_P_IP)) {
  		struct brnf_frag_data *data;
  
  		if (br_validate_ipv4(net, skb))
  			goto drop;
  
  		IPCB(skb)->frag_max_size = nf_bridge->frag_max_size;
  
  		nf_bridge_update_protocol(skb);
  
  		data = this_cpu_ptr(&brnf_frag_data_storage);
  
  		data->vlan_tci = skb->vlan_tci;
  		data->vlan_proto = skb->vlan_proto;
  		data->encap_size = nf_bridge_encap_header_len(skb);
  		data->size = ETH_HLEN + data->encap_size;
  
  		skb_copy_from_linear_data_offset(skb, -data->size, data->mac,
  						 data->size);
  
  		return br_nf_ip_fragment(net, sk, skb, br_nf_push_frag_xmit);
  	}
  	if (IS_ENABLED(CONFIG_NF_DEFRAG_IPV6) &&
  	    skb->protocol == htons(ETH_P_IPV6)) {
  		const struct nf_ipv6_ops *v6ops = nf_get_ipv6_ops();
  		struct brnf_frag_data *data;
  
  		if (br_validate_ipv6(net, skb))
  			goto drop;
  
  		IP6CB(skb)->frag_max_size = nf_bridge->frag_max_size;
  
  		nf_bridge_update_protocol(skb);
  
  		data = this_cpu_ptr(&brnf_frag_data_storage);
  		data->encap_size = nf_bridge_encap_header_len(skb);
  		data->size = ETH_HLEN + data->encap_size;
  
  		skb_copy_from_linear_data_offset(skb, -data->size, data->mac,
  						 data->size);
  
  		if (v6ops)
  			return v6ops->fragment(net, sk, skb, br_nf_push_frag_xmit);
  
  		kfree_skb(skb);
  		return -EMSGSIZE;
  	}
  	nf_bridge_info_free(skb);
  	return br_dev_queue_push_xmit(net, sk, skb);
   drop:
  	kfree_skb(skb);
  	return 0;
  }
  
  /* PF_BRIDGE/POST_ROUTING ********************************************/
  static unsigned int br_nf_post_routing(void *priv,
  				       struct sk_buff *skb,
  				       const struct nf_hook_state *state)
  {
  	struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
  	struct net_device *realoutdev = bridge_parent(skb->dev);
  	u_int8_t pf;
  
  	/* if nf_bridge is set, but ->physoutdev is NULL, this packet came in
  	 * on a bridge, but was delivered locally and is now being routed:
  	 *
  	 * POST_ROUTING was already invoked from the ip stack.
  	 */
  	if (!nf_bridge || !nf_bridge->physoutdev)
  		return NF_ACCEPT;
  
  	if (!realoutdev)
  		return NF_DROP;
  
  	if (IS_IP(skb) || IS_VLAN_IP(skb) || IS_PPPOE_IP(skb))
  		pf = NFPROTO_IPV4;
  	else if (IS_IPV6(skb) || IS_VLAN_IPV6(skb) || IS_PPPOE_IPV6(skb))
  		pf = NFPROTO_IPV6;
  	else
  		return NF_ACCEPT;
  
  	/* We assume any code from br_dev_queue_push_xmit onwards doesn't care
  	 * about the value of skb->pkt_type. */
  	if (skb->pkt_type == PACKET_OTHERHOST) {
  		skb->pkt_type = PACKET_HOST;
  		nf_bridge->pkt_otherhost = true;
  	}
  
  	nf_bridge_pull_encap_header(skb);
  	if (pf == NFPROTO_IPV4)
  		skb->protocol = htons(ETH_P_IP);
  	else
  		skb->protocol = htons(ETH_P_IPV6);
  
  	NF_HOOK(pf, NF_INET_POST_ROUTING, state->net, state->sk, skb,
  		NULL, realoutdev,
  		br_nf_dev_queue_xmit);
  
  	return NF_STOLEN;
  }
  
  /* IP/SABOTAGE *****************************************************/
  /* Don't hand locally destined packets to PF_INET(6)/PRE_ROUTING
   * for the second time. */
  static unsigned int ip_sabotage_in(void *priv,
  				   struct sk_buff *skb,
  				   const struct nf_hook_state *state)
  {
  	if (skb->nf_bridge && !skb->nf_bridge->in_prerouting &&
  	    !netif_is_l3_master(skb->dev)) {
  		state->okfn(state->net, state->sk, skb);
  		return NF_STOLEN;
  	}
  
  	return NF_ACCEPT;
  }
  
  /* This is called when br_netfilter has called into iptables/netfilter,
   * and DNAT has taken place on a bridge-forwarded packet.
   *
   * neigh->output has created a new MAC header, with local br0 MAC
   * as saddr.
   *
   * This restores the original MAC saddr of the bridged packet
   * before invoking bridge forward logic to transmit the packet.
   */
  static void br_nf_pre_routing_finish_bridge_slow(struct sk_buff *skb)
  {
  	struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
  
  	skb_pull(skb, ETH_HLEN);
  	nf_bridge->bridged_dnat = 0;
  
  	BUILD_BUG_ON(sizeof(nf_bridge->neigh_header) != (ETH_HLEN - ETH_ALEN));
  
  	skb_copy_to_linear_data_offset(skb, -(ETH_HLEN - ETH_ALEN),
  				       nf_bridge->neigh_header,
  				       ETH_HLEN - ETH_ALEN);
  	skb->dev = nf_bridge->physindev;
  
  	nf_bridge->physoutdev = NULL;
  	br_handle_frame_finish(dev_net(skb->dev), NULL, skb);
  }
  
  static int br_nf_dev_xmit(struct sk_buff *skb)
  {
  	if (skb->nf_bridge && skb->nf_bridge->bridged_dnat) {
  		br_nf_pre_routing_finish_bridge_slow(skb);
  		return 1;
  	}
  	return 0;
  }
  
  static const struct nf_br_ops br_ops = {
  	.br_dev_xmit_hook =	br_nf_dev_xmit,
  };
  
  void br_netfilter_enable(void)
  {
  }
  EXPORT_SYMBOL_GPL(br_netfilter_enable);
  
  /* For br_nf_post_routing, we need (prio = NF_BR_PRI_LAST), because
   * br_dev_queue_push_xmit is called afterwards */
  static const struct nf_hook_ops br_nf_ops[] = {
  	{
  		.hook = br_nf_pre_routing,
  		.pf = NFPROTO_BRIDGE,
  		.hooknum = NF_BR_PRE_ROUTING,
  		.priority = NF_BR_PRI_BRNF,
  	},
  	{
  		.hook = br_nf_forward_ip,
  		.pf = NFPROTO_BRIDGE,
  		.hooknum = NF_BR_FORWARD,
  		.priority = NF_BR_PRI_BRNF - 1,
  	},
  	{
  		.hook = br_nf_forward_arp,
  		.pf = NFPROTO_BRIDGE,
  		.hooknum = NF_BR_FORWARD,
  		.priority = NF_BR_PRI_BRNF,
  	},
  	{
  		.hook = br_nf_post_routing,
  		.pf = NFPROTO_BRIDGE,
  		.hooknum = NF_BR_POST_ROUTING,
  		.priority = NF_BR_PRI_LAST,
  	},
  	{
  		.hook = ip_sabotage_in,
  		.pf = NFPROTO_IPV4,
  		.hooknum = NF_INET_PRE_ROUTING,
  		.priority = NF_IP_PRI_FIRST,
  	},
  	{
  		.hook = ip_sabotage_in,
  		.pf = NFPROTO_IPV6,
  		.hooknum = NF_INET_PRE_ROUTING,
  		.priority = NF_IP6_PRI_FIRST,
  	},
  };
  
  static int brnf_device_event(struct notifier_block *unused, unsigned long event,
  			     void *ptr)
  {
  	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
  	struct brnf_net *brnet;
  	struct net *net;
  	int ret;
  
  	if (event != NETDEV_REGISTER || !(dev->priv_flags & IFF_EBRIDGE))
  		return NOTIFY_DONE;
  
  	ASSERT_RTNL();
  
  	net = dev_net(dev);
  	brnet = net_generic(net, brnf_net_id);
  	if (brnet->enabled)
  		return NOTIFY_OK;
  
  	ret = nf_register_net_hooks(net, br_nf_ops, ARRAY_SIZE(br_nf_ops));
  	if (ret)
  		return NOTIFY_BAD;
  
  	brnet->enabled = true;
  	return NOTIFY_OK;
  }
  
  static void __net_exit brnf_exit_net(struct net *net)
  {
  	struct brnf_net *brnet = net_generic(net, brnf_net_id);
  
  	if (!brnet->enabled)
  		return;
  
  	nf_unregister_net_hooks(net, br_nf_ops, ARRAY_SIZE(br_nf_ops));
  	brnet->enabled = false;
  }
  
  static struct pernet_operations brnf_net_ops __read_mostly = {
  	.exit = brnf_exit_net,
  	.id   = &brnf_net_id,
  	.size = sizeof(struct brnf_net),
  };
  
  static struct notifier_block brnf_notifier __read_mostly = {
  	.notifier_call = brnf_device_event,
  };
  
  /* recursively invokes nf_hook_slow (again), skipping already-called
   * hooks (< NF_BR_PRI_BRNF).
   *
   * Called with rcu read lock held.
   */
  int br_nf_hook_thresh(unsigned int hook, struct net *net,
  		      struct sock *sk, struct sk_buff *skb,
  		      struct net_device *indev,
  		      struct net_device *outdev,
  		      int (*okfn)(struct net *, struct sock *,
  				  struct sk_buff *))
  {
  	const struct nf_hook_entries *e;
  	struct nf_hook_state state;
  	struct nf_hook_ops **ops;
  	unsigned int i;
  	int ret;
  
  	e = rcu_dereference(net->nf.hooks_bridge[hook]);
  	if (!e)
  		return okfn(net, sk, skb);
  
  	ops = nf_hook_entries_get_hook_ops(e);
  	for (i = 0; i < e->num_hook_entries &&
  	      ops[i]->priority <= NF_BR_PRI_BRNF; i++)
  		;
  
  	nf_hook_state_init(&state, hook, NFPROTO_BRIDGE, indev, outdev,
  			   sk, net, okfn);
  
  	ret = nf_hook_slow(skb, &state, e, i);
  	if (ret == 1)
  		ret = okfn(net, sk, skb);
  
  	return ret;
  }
  
  #ifdef CONFIG_SYSCTL
  static
  int brnf_sysctl_call_tables(struct ctl_table *ctl, int write,
  			    void __user *buffer, size_t *lenp, loff_t *ppos)
  {
  	int ret;
  
  	ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
  
  	if (write && *(int *)(ctl->data))
  		*(int *)(ctl->data) = 1;
  	return ret;
  }
  
  static struct ctl_table brnf_table[] = {
  	{
  		.procname	= "bridge-nf-call-arptables",
  		.data		= &brnf_call_arptables,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= brnf_sysctl_call_tables,
  	},
  	{
  		.procname	= "bridge-nf-call-iptables",
  		.data		= &brnf_call_iptables,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= brnf_sysctl_call_tables,
  	},
  	{
  		.procname	= "bridge-nf-call-ip6tables",
  		.data		= &brnf_call_ip6tables,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= brnf_sysctl_call_tables,
  	},
  	{
  		.procname	= "bridge-nf-filter-vlan-tagged",
  		.data		= &brnf_filter_vlan_tagged,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= brnf_sysctl_call_tables,
  	},
  	{
  		.procname	= "bridge-nf-filter-pppoe-tagged",
  		.data		= &brnf_filter_pppoe_tagged,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= brnf_sysctl_call_tables,
  	},
  	{
  		.procname	= "bridge-nf-pass-vlan-input-dev",
  		.data		= &brnf_pass_vlan_indev,
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.proc_handler	= brnf_sysctl_call_tables,
  	},
  	{ }
  };
  #endif
  
  static int __init br_netfilter_init(void)
  {
  	int ret;
  
  	ret = register_pernet_subsys(&brnf_net_ops);
  	if (ret < 0)
  		return ret;
  
  	ret = register_netdevice_notifier(&brnf_notifier);
  	if (ret < 0) {
  		unregister_pernet_subsys(&brnf_net_ops);
  		return ret;
  	}
  
  #ifdef CONFIG_SYSCTL
  	brnf_sysctl_header = register_net_sysctl(&init_net, "net/bridge", brnf_table);
  	if (brnf_sysctl_header == NULL) {
  		printk(KERN_WARNING
  		       "br_netfilter: can't register to sysctl.\n");
  		unregister_netdevice_notifier(&brnf_notifier);
  		unregister_pernet_subsys(&brnf_net_ops);
  		return -ENOMEM;
  	}
  #endif
  	RCU_INIT_POINTER(nf_br_ops, &br_ops);
  	printk(KERN_NOTICE "Bridge firewalling registered\n");
  	return 0;
  }
  
  static void __exit br_netfilter_fini(void)
  {
  	RCU_INIT_POINTER(nf_br_ops, NULL);
  	unregister_netdevice_notifier(&brnf_notifier);
  	unregister_pernet_subsys(&brnf_net_ops);
  #ifdef CONFIG_SYSCTL
  	unregister_net_sysctl_table(brnf_sysctl_header);
  #endif
  }
  
  module_init(br_netfilter_init);
  module_exit(br_netfilter_fini);
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Lennert Buytenhek <buytenh@gnu.org>");
  MODULE_AUTHOR("Bart De Schuymer <bdschuym@pandora.be>");
  MODULE_DESCRIPTION("Linux ethernet netfilter firewall bridge");
  